they are both very similar, the geforce certainly isn't powerful enough to utilise all of the memory that it has. If you are serious about your gaming I would look powerful graphics card than either of them. Neither will be able to play any modern games at anywhere near their maximum settings. Perhaps look as fitting a second hand geforce 480, 560 or 570 if your budget is limited.
Best Cyber Monday deals 2015 live blog: Best UK Cyber Monday tech deals, sales, discounts & offers